Liquid crystal display devices equipped with a liquid crystal display panel are used in various electronic devices such as smart phones and tablet terminals. In addition to the liquid crystal display panel, the liquid crystal display device includes a lighting device (backlight device) for supplying light to the liquid crystal display panel.
Lighting devices known as edge light (or side light) type are known, in which light sources are disposed opposite an end face of a light guide plate. In this type of lighting device, a plurality of LEDs (Light Emitting Diodes) are mounted in single file on a flexible substrate such as an FPC (Flexible Printed Circuit) and used as a light source unit, as shown in Patent Document 1.
In this light source unit, the anode terminals and cathode terminals of the LEDs are each electrically connected to wiring patterns provided on the flexible substrate by soldering. The wiring patterns are formed on an insulating support base member that forms the flexible substrate, and covered by a cover lay that is an insulating film. The wiring patterns include anode-side wiring patterns connected to anode terminals and cathode-side wiring patterns connected to cathode terminals, and these wiring patterns are exposed through openings formed in the cover lay and soldered to the anode and cathode terminals of the LEDs.
The solder in portions connecting the respective terminals of the LEDs and the wiring patterns is positioned inside the openings in such a way as to adhere to the edges of the openings in the cover lay.